The present invention relates to a gas spring of the type in which a piston assembly carried on the end of a rod slides back and forth in a cylinder so that extending and retracting the rod expands and contracts the spring. The cylinder is sealed at the head end and sealing means also is provided between the rod and the cylinder and the cylinder is filled with a fluid under pressure. The piston assembly is such that the passage of pressure fluid from one side to the other is restricted as the spring is expanded and this results in a dampening action but the restriction is eliminated when the spring is contracted so that there is virtually no dampening effect. A gas spring of this general type is shown in Wustenhagen et al U.S. Pat. No. 3,207,498.